The present invention relates generally to the field of fluid storage tanks, and more particularly to the field of water storage tanks for use in the cooling system of a motorized vehicle or a stationary power plant.
Self-propelled vehicles such as automobiles and locomotive are known to incorporate a cooling system for the engine of the vehicle. Such cooling systems may contain a water storage tank formed as part of a radiator or as a separate tank in fluid communication with a radiator. In order to increase the temperature at which the water may be maintained without boiling, the water storage tank may be maintained at a pressure that is higher than the ambient atmospheric pressure. Such water storage tanks typically include an inlet opening which is sealed during operation by a pressure cap. A danger exists if an operator removes the pressure cap while the cooling system is pressurized. For railroad locomotive applications, it is known to incorporate a bypass line and relief valve in the fill tube of such a water tank to relieve pressure prior to opening the fill cap. It is further known to incorporate a mechanism that requires the relief valve to be placed in its open position prior to the removal of the pressure cap. However, there is no mechanism to prevent the pressure cap from being removed before all of the pressure in the tank is relieved. Furthermore, in some applications a radiator or other cooling system component may be located above the height of the cap, so if there is water in the radiator when the cap is removed, gravity alone may force a backflow through the fill tube.
It is also common practice to introduce corrosion inhibiting chemicals into the cooling system of a self-propelled vehicle. For automobile applications, such chemicals are often incorporated into the cooling fluid in a liquid form. For locomotive applications, it is known to introduce such chemicals in a solid form into the water storage tank. For example, granular alkaline salt may be added to maintain the cooling water pH at the desired high level. The granular material slowly dissolves into the cooling fluid, thus providing a desired level of water treatment over an period of time. Make-up fluid and chemical additives must be periodically added to the cooling system, thereby necessitating periodic removal of the pressure cap of the tank.